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Phenotypic and integrated analysis of a comprehensive Pseudomonas aeruginosa PAO1 library of mutants lacking cyclic-di-GMP-related genes

ABSTRACT: Pseudomonas aeruginosa is a Gram-negative bacterium able to survive and adapt in a multitude of niches as well as thriving within many different hosts. This versatility lies within a large genome of ca 6Mbp and a tight control in the expression of thousands of genes. Among the regulatory mechanisms widely spread in bacteria, cyclic-di-GMP signaling is one which influences all levels of control. It is made by diguanylate cyclases and broken by phosphodiesterases while the intracellular level of this molecule drives phenotypic responses. The signaling involve modification of enzymes or proteins function upon c-di-GMP binding, including modifying the activity of regulators which in turn will impact the transcriptome. In P. aeruginosa, there are ca 40 genes encoding putative DGC or PDE. The combined activity of those enzymes should reflect the c-di-GMP concentration while specific phenotypic output could be correlated to a given set of dgc/pde. This notion of specificity has been addressed in several studies and different strains of P. aeruginosa. Here, we engineered a mutant library for the 41 individual dgc/pde genes in P. aeruginosa PAO1. In most cases, we observed a significant to slight variation in the global c-di-GMP pool, with essentially an impact on biofilm phenotypes including initial attachment and maturation, while very little is observed on motility which differs from previous studies. We observe that minor changes in c-di-GMP level have a drastic phenotypic impact thus supporting the idea of local vs global c-di-GMP pool. Our RNA-seq analysis indicates that all PAO1 dgc/pde genes are expressed in both planktonic and biofilm growth conditions and our work suggests that c-di-GMP networks owe to be reconstructed in one single strain and cannot be built by cross-comparison with studies in other strains.

ORGANISM(S): Pseudomonas aeruginosa

PROVIDER: GSE203348 | GEO | 2022/05/23

REPOSITORIES: GEO

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Project description:Bacterial lifestyles are dictated by the conditions encountered during colonization of a specific ecological niche or host. A wide range of environmental stimuli triggers sensory modules, that modify activity of proteins, or/and initiate a transfer of information in complex regulatory networks, which modulate gene expression, and therefore adaptation. The transition between planktonic and biofilm growth is dependent on the homeostasis of the intracellular second messenger c-di-GMP. High c-di-GMP levels driven by diguanylate cyclase (DGC) activity favor biofilm while low levels maintained by phosphodiesterase (PDE) enzymes encourage planktonic style or biofilm dispersal. In Pseudomonas aeruginosa over 40 PDE/DGC are involved in c-di-GMP homeostasis, including 16 dual enzymes possessing both canonical DGC and PDE motifs, i.e. GGDEF and EAL, respectively. It has been previously reported that the deletion of the PDE/DGC dual enzyme PA0285, one of 5 c-di-GMP-related enzymes conserved across all Pseudomonas species, impacts biofilms and causes elevated c-di-GMP levels in P. aeruginosa. Here we confirm that this role is conserved in various P. aeruginosa (PAO1, PA14 and PAK) and Pseudomonas putida strains. Deletion of PA0285 has the highest impact during the early stage of surface colonization, and RNA-seq analysis in biofilm context indicates that it may be associated with upregulation of cupA fimbrial genes. We demonstrate that the C-terminal portion of PA0285 encompassing the GGDEF and EAL domains binds the respective GTP (GGDEF) and c-di-GMP (EAL) substrates but only exhibits PDE activity in vitro. Both GGDEF and EAL domains are important for PA0285 PDE activity in vivo as suggested by site-directed mutants in each of the key motifs. Complementation of the PA0285 mutant strain with the C-terminal GGDEF/EAL portion in trans is not as effective as with the full-length gene suggesting that the transmembrane region and PAS domains contained in PA0285’s N-terminal portion influence its PDE activity in vivo. We speculate that the transmembrane portion or/and PAS domains of PA0285 impede its PDE activity in vivo through modulating the conformation of the enzyme, as shown for P. aeruginosa RbdA, in response to an unknown stimulus.

Project description:Francisella tularensis is a Gram-negative bacterium that is highly virulent in humans, causing the disease tularemia. F. novicida is closely related to F. tularensis and exhibits high virulence in mice, but is avirulent in healthy humans. A F. novicida-specific gene cluster (FTN0451-FTN0456) encodes two proteins with diguanylate cyclase (DGC) and phosphodiesterase (PDE) domains that modulate synthesis and degradation of cyclic di-GMP (cdGMP). No DGC or PDE containing proteins are present in the F. tularensis genome. F. novicida strains lacking either the two DGC/PDE genes cdgA and cdgB or the entire gene cluster (KKF457) are defective for biofilm formation. In addition, expression of CdgB or a heterologous DGC in KKF457 stimulated F. novicida biofilms, even in a strain lacking the biofilm regulator QseB. Genetic evidence suggests that CdgA is predominantly a PDE, while CdgB is predominantly a DGC. The F. novicida qseB strain has reduced cdgA and cdgB transcript levels, demonstrating a F. novicida biofilm signaling cascade that controls cdGMP levels. Interestingly, KKF457 with elevated cdGMP levels exhibited a decrease in intramacrophage replication and virulence in mice, as well as increased growth yield and biofilm formation in vitro. Microarray analyses revealed that cdGMP stimulated the transcription of a chitinase (ChiB) known to contribute to biofilm formation. Our results indicate that elevated cdGMP in F. novicida stimulates biofilm formation and inhibits virulence. We suggest that differences in human virulence between F. novicida and F. tularensis may be due in part to the absence of cdGMP signaling in F. tularensis. A whole genome NibleGen microarray was developed for multiple Francisella subspecies, using shared probes for common genes as well as unique probes for subspecies-specific genes. Included were probes representing the F. novicida U112 genome, with a maximum of 6 probes/gene. RNA was isolated from bacteria and purified as described above. The double-strand cDNA was generated and labeled with Cy3 according to the NimbleGen Gene Expression Array protocol (www.nimblegen.com), using SuperScript Double-Stranded cDNA Synthesis Kit (Invitrogen) and the DNA Labeling Kit (NimbleGen). Microarray results were analyzed using the ArrayStar software (DNASTAR).

Project description:Transcriptional profiles of Escherichia coli MG1655 in mixed culture with Pseudomonas aeruginosa PAO1 showed a number of E. coli genes to be upregulated including purA-F and other genes associated with purine synthesis. In contrast, genes associated with pyrimidine synthesis were unaffected. Competition experiments in both planktonic and biofilm cultures, using three purine synthesis mutants, purD, purH, and purT showed little difference in E. coli survival from the parent strain. As purines are components of the cell signals, cAMP and c-di-GMP, we conducted competition experiments with E. coli mutants lacking adenylate cyclase (cyaA), cAMP phosphodiesterase (cpdA), and the catabolite receptor protein (crp), as well as ydeH, an uncharacterized gene that has been associated with c-di-GMP synthesis. Survival of the cyaA and crp mutants during co-culture were significantly less than the parent strain. Supplementation of the media with 1mM cAMP could restore survival of the cyaA mutant but not the crp mutant. In contrast, survival of the cpdA mutant was similar to the parent strain. Survival of the ydeH mutant was moderately less than the parent, suggesting that cAMP has more impact on E. coli mixed culture growth than c-di-GMP. Addition of 1 mM indole restored the survival of both the cyaA and crp mutations. Mutants in genes for tryptophan synthesis (trpE) and indole production (tnaA) showed a loss of competition and recovery through indole supplementation, comparable to the cyaA and crp mutants. Overall, these results suggest indole and cAMP as major contributing factors to E. coli growth in mixed culture. Two replicates of LB grown E. coli ZK126 and P. aeruginosa PAO1 were grown in pure culture at 37C to an OD of 0.3 (log phase) and then mixed 1:1 and incubated for an additional 45 min. RNA was extracted, purified, reverse transcribed to cDNA and then analyzed on E. coli and P. aeruginosa chips from Affymetrix. Expression profiles were compared to pure culture E. coli and P. aeruginosa grown on LB.

Project description:Transcriptional profiles of Escherichia coli MG1655 in mixed culture with Pseudomonas aeruginosa PAO1 showed a number of E. coli genes to be upregulated including purA-F and other genes associated with purine synthesis. In contrast, genes associated with pyrimidine synthesis were unaffected. Competition experiments in both planktonic and biofilm cultures, using three purine synthesis mutants, purD, purH, and purT showed little difference in E. coli survival from the parent strain. As purines are components of the cell signals, cAMP and c-di-GMP, we conducted competition experiments with E. coli mutants lacking adenylate cyclase (cyaA), cAMP phosphodiesterase (cpdA), and the catabolite receptor protein (crp), as well as ydeH, an uncharacterized gene that has been associated with c-di-GMP synthesis. Survival of the cyaA and crp mutants during co-culture were significantly less than the parent strain. Supplementation of the media with 1mM cAMP could restore survival of the cyaA mutant but not the crp mutant. In contrast, survival of the cpdA mutant was similar to the parent strain. Survival of the ydeH mutant was moderately less than the parent, suggesting that cAMP has more impact on E. coli mixed culture growth than c-di-GMP. Addition of 1 mM indole restored the survival of both the cyaA and crp mutations. Mutants in genes for tryptophan synthesis (trpE) and indole production (tnaA) showed a loss of competition and recovery through indole supplementation, comparable to the cyaA and crp mutants. Overall, these results suggest indole and cAMP as major contributing factors to E. coli growth in mixed culture. E. coli MG1655 and P. aeruginosa PAO1 were grown in a minimal defined medium containing N-acetyl glucosamine, overnight at 37C to an OD of 1.5, and then inoculated in fresh media at an OD of 0.001 and grown in pure or mixed culture for 4-5 hours to a final OD of 0.5. RNA was extracted, purified, reverse transcribed to cDNA and then analyzed on E. coli and P. aeruginosa chips from Affymetrix. Expression profiles of mixed culture-grown organisms were compared to pure culture E. coli and P. aeruginosa grown on the same defined medium.

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Phenotypic and integrated analysis of a comprehensive Pseudomonas aeruginosa PAO1 library of mutants lacking cyclic-di-GMP-related genes

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